Malignant Pilomatricoma: A Report of Two Cases and Review of Literature

Malignant Pilomatricoma of the Lower Extremity: A Difficult and Rare Diagnosis

“…Both benign and malignant pilomatricomas exhibit nests of basaloid cells and eosinophilic, enucleated ghost cells. The additional presence of nuclear pleomorphism, cellular atypia, numerous mitoses, and areas of necrosis with contiguous desmoplasia can help differentiate the tumors [1][2][3]5]. Interestingly, intralesional calcification and giant cells occur rarely in these tumors, with a review of 35 different malignant pilomatricoma lesions revealing four and one cases with these findings, respectively [4].…”

“…Increased rate of recurrence is associated with higher rate of metastasis with the most common sites being regional lymph nodes and lungs [1,2]. Although systemic chemotherapy has not proven to be beneficial, adjunctive radiotherapy may be considered in cases of recurrence or metastasis [3].…”

“…Although only about 130 cases have been documented in English literature, malignant pilomatricomas are clinically important as they demonstrate locally aggressive behavior with a strong tendency to recur and metastasize [ 1 , 2 ]. Also known as pilomatrix carcinomas, most malignant pilomatricomas arise on the head and neck region, predominantly affect Caucasian males, and have a bimodal distribution in the sixth and seventh decades and the first three decades [ 3 , 4 ]. Only 11% of cases have been documented to occur on the lower extremity, as in this patient [ 3 ].…”

“…Also known as pilomatrix carcinomas, most malignant pilomatricomas arise on the head and neck region, predominantly affect Caucasian males, and have a bimodal distribution in the sixth and seventh decades and the first three decades [ 3 , 4 ]. Only 11% of cases have been documented to occur on the lower extremity, as in this patient [ 3 ]. Typical presentation includes a solitary, slow-growing, and firm subcutaneous lesion that is often misdiagnosed for its benign equivalent due to similar histologic findings [ 5 ].…”

“…Increased rate of recurrence is associated with higher rate of metastasis with the most common sites being regional lymph nodes and lungs [ 1 , 2 ]. Although systemic chemotherapy has not proven to be beneficial, adjunctive radiotherapy may be considered in cases of recurrence or metastasis [ 3 ]. Given the importance of correct diagnosis to surveil for recurrence and metastasis, we encourage continued work to develop high-quality evidence in the pathogenesis and treatment of malignant pilomatricoma.…”