Keywords malignant pilomatricoma - lung metastasis - case reports
Introduction
Malignant pilomatricoma is a rare malignant tumor that originates from hair follicles
and is infrequently encountered in clinical practice. Due to its overlapping histological
features with benign pilomatricoma, it can be easily misdiagnosed, leading to a delayed
diagnosis. When treating a patient with malignant pilomatricoma, the plastic surgeon
must plan for surgery while taking into account the tumor's aggressiveness and potential
for distant metastasis. It is important to recognize this entity, as malignant pilomatricoma
can recur if not completely excised and may metastasize to the lungs, bones, and lymph
nodes. We report our experience with a patient diagnosed with malignant pilomatricoma
with lung metastasis who underwent wide local excision for a lesion on the flank.
The patient provided written informed consent for the publication of this report and
all accompanying images.[1 ]
[2 ]
Case
An 84-year-old man presented to our clinic with a palpable mass on his left flank.
The mass was quite large and protruding, and no other cutaneous symptoms were observed.
The patient did not remember exactly when the lump had been present, but he said it
had been palpable for months, and there was a significant weight loss at the time.
The mass was large enough to be clearly visible to the naked eye, had no tenderness,
and showed no clinical symptoms other than weight loss. Prior to his visit, computed
tomography (CT) scans and ultrasonography were performed at other hospitals. The CT
scans revealed a huge mass measuring 4.5 × 2.2 cm in the flank, with reports suggesting
possible malignancy ([Fig. 1 ]). CT also showed a spiculated mass in the right upper lobe, which was suspicious
for lung cancer ([Fig. 2 ]). Ultrasonography showed a heterogeneously hypoechoic subcutaneous mass lesion with
prominently increased vascularity and perilesional soft tissue edematous changes ([Fig. 3 ]).
Fig. 1 Computed tomography scans revealed a huge mass measuring 4.5 × 2.2 cm in the flank,
with reports suggesting possible malignancy.
Fig. 2 Computed tomography scans revealed a spiculated mass with infected bullae measuring
3.3 cm in the right upper lobe, with reports suggesting possible malignancy.
Fig. 3 Ultrasound revealed a heterogeneously hypoechoic subcutaneous mass lesion with prominently
increased vascularity and perilesional soft tissue edematous changes.
Upon initial examination, a large protruding lump was identified on the patient's
flank ([Fig. 4A ]). Consequently, wide local excision of the mass on the left flank and a local advancement
flap under local anesthesia were planned. The proposed incision line was marked with
gentian violet solution around the mass on the left flank. Using a no. 15 surgical
blade, the mass was excised with 10-mm safety margin along the proposed incision line,
revealing multiple pieces of grayish-brown tissue. The excised specimen was sent to
our pathology department for frozen biopsy, the results of which indicated that all
margins were negative for malignancy. Since the skin flap could be moved directly
toward the defect, the flap was elevated and advanced ([Fig. 4B ]).
Fig. 4 (A ) A large protruding lump was identified. (B ) Postoperative view after wide local excision.
This patient was initially suspected to have lung cancer, and we were requested to
perform surgery for a cutaneous metastatic mass. After wide local excision, however,
malignant pilomatricoma was diagnosed based on the biopsy results. Furthermore, this
cutaneous mass was confirmed to be the primary cancer from which the lung metastases
originated.
Permanent histopathology revealed malignant pilomatricoma with hair follicular differentiation
as a malignant skin adnexal tumor. The tumor was composed of hyperchromatic basaloid
cells and infiltrates on the periphery ([Fig. 5A ]). The pathologic findings also included basaloid tumor cells exhibiting significant
cytologic atypia and frequent mitosis with ghost cells, consistent with malignant
pilomatricoma ([Fig. 5B ]). Immunohistochemistry was not only strongly positive for creatine kinase and epithelial
membrane antigen but also focally positive for thyroid transcription factor-1, synaptophysin,
CD56, and chromogranin. Further evaluations, including a bone scan, whole-body positron
emission tomography/CT, and chest CT, were performed to rule out additional distant
metastasis, and no further metastasis was identified.
Fig. 5 Histological findings of malignant pilomatricoma. (A ) At low magnification, the tumor displayed hyperchromatic basaloid cells and infiltrates
on the periphery (arrowhead ). (B ) In a high-power image, the basaloid tumor cells exhibited significant cytologic
atypia and frequent mitosis (indicated by arrows ) along with ghost cells (denoted by an asterisk ). Original magnification: (A ) ×20; (B ) ×400.
To treat the lung metastasis, a video-assisted thoracoscopic biopsy of the lung lesion
was done, which confirmed metastasis from the primary cancer on the flank. Several
courses of chemotherapy with intravenous cisplatin and 5-fluorouracil were given.
Follow-up CT after each cycle showed shrinkage of the lung metastasis. During the
follow-up period, the patient regularly visited our clinic and experienced no issues.
After surgery, the patient recovered well without any complications. At the 6-week
follow-up, the patient carried on with daily life without difficulties and was able
to receive medical treatment for lung metastasis.
Discussion
Malignant pilomatricoma originates from hair follicles and is very rare in clinical
practice. It presents as an asymptomatic, potentially ulcerative, enveloped subcutaneous
nodule or cystic mass, and it cannot be reliably distinguished from benign adnexal
tumors based on clinical appearance alone.[3 ]
[4 ]
[5 ]
[6 ]
Malignant pilomatricomas are primarily observed in elderly individuals between their
sixth and seventh decades of life, with a male-to-female ratio of 5:1.[7 ] These tumors most commonly occur on the head, neck, and back, ranging in size from
1 to 10 cm, and are typically located in the deep dermis.[2 ]
[4 ] In the present case, the mass was discovered on the patient's flank as a visibly
protruding lump that could be seen with the naked eye.
In some instances, malignant pilomatricoma has been misdiagnosed as benign pilomatricoma,
leading to a delayed diagnosis; occasionally, it has been misidentified as a vascular
malformation.[3 ] It can be confused between malignant and benign pilomatricoma since both have features
of slow progression and firm subcutaneous lesions.[1 ]
Diagnosing malignant pilomatricoma can be challenging due to the lack of distinct
histologic criteria that differentiate it from benign pilomatricoma.[2 ]
[3 ]
[8 ] Both benign and malignant pilomatricomas exhibit nests of basaloid and eosinophilic,
enucleated ghost cells.[1 ]
[2 ]
[8 ] However, nuclear polymorphisms, atypical cells, multiple mitoses, and necrosis with
serial desmoplasia can aid in distinguishing malignant tumors from their benign counterparts.[1 ]
[4 ]
[6 ] Malignant pilomatricoma also presents with poor circumscription; infiltration of
the hypodermis, dermis, and cartilage; and occasionally perineural or vascular invasion.[2 ] This malignancy is characterized by the proliferation of large, anaplastic hyperchromatic
basophilic cells with numerous mitoses in various areas, particularly around the tumor's
peripheral region, as demonstrated in this case.[4 ]
[6 ] Malignant pilomatricoma can be differentiated from benign tumors by its aggressive
features, bony invasion, rare metastasis, and tendency to recur, especially when incompletely
excised.[3 ]
[4 ]
[6 ]
[8 ]
The description of histopathology results should encompass the presence of necrosis,
atypical mitotic counts, and the occurrence of perineural or vascular invasion.[1 ]
[2 ] Additionally, it is crucial to include the depth of invasion, as poorly differentiated
tumors with extensive soft tissue invasion are associated with a poor prognosis.[2 ]
[7 ]
No specific immunohistochemical marker for malignant pilomatricoma has yet been confirmed.
In this case, the mass was strongly positive for creatine kinase and epithelial membrane
antigen.[1 ]
[8 ]
Due to the rarity of malignant pilomatricoma, no clear criteria have been established
for its surgical management, nor do clear recommendations exist regarding the width
of the surgical margin.[8 ] Based on the limited number of cases reported thus far, a high likelihood of recurrence
has been observed when only a simple excision is performed. However, research has
confirmed that the recurrence rate is significantly reduced when wide local excision
is performed with a safety margin of at least ≥5 mm.[1 ]
[2 ]
[4 ]
[6 ]
[9 ]
When developing a treatment plan, it is important to consider the high recurrence
rate of malignant pilomatricoma while also noting that distant metastasis is rare.
Distant metastases have been reported in approximately 10% of cases, primarily affecting
the lungs, bones, regional lymph nodes, and visceral organs, and proving fatal in
these instances.[6 ]
[7 ] It can disseminate via the lymphatic or the blood system, and although metastases
were initially considered to be exceptional, this contributes to the increase of cases
of metastasis. Following surgical treatment, radiotherapy is recommended for cases
involving recurrence or residual macroscopic tumors.[1 ]
[2 ]
[4 ] However, no established chemotherapy regimen has been demonstrated to be effective
in slowing or preventing the progression of malignant pilomatricoma.[7 ] To the best of our knowledge, systemic chemotherapy has been tried in several cases
of malignant pilomatricoma with multiple metastases, and most cases did not respond
to treatment.[10 ] In some cases, however, follow-up chest CT scans showed partial response of metastatic
lung lesions after each course of cisplatin and 5-fluorouracil.[11 ]
Malignant pilomatricoma is a rare cutaneous tumor typically found on the head and
neck; however, in the present case, it was located on the flank. Diagnosing malignant
pilomatricoma can be challenging due to the lack of clear histologic criteria to differentiate
it from benign pilomatricoma. For treatment, wide local excision may be sufficient
for this carcinoma. Additionally, adjunctive radiotherapy and chemotherapy can be
considered in cases of recurrence or metastasis, with the most common locations for
metastasis being regional lymph nodes and the lungs.
Malignant pilomatricoma is a rare cutaneous malignancy that is typically found on
the head and neck. However, in the case presented herein, it was located on the flank
and showed intralesional calcification and multinucleated giant cells. This carcinoma
can be treated with wide local excision. Adjunctive radiotherapy can be considered
in cases of recurrence or metastasis. The most common locations of metastasis are
the regional lymph nodes and the lungs. In the cases with lung metastasis, chemotherapy
with cisplatin and 5-fluorouracil can be considered.
