Anaplastic large cell lymphoma: a potential pitfall in the differential diagnosis of melanoma.
The diagnosis of metastatic melanoma can be complicated by absent characteristic cytology, melanin, or antigen expression in a suspect tumor, putting the pathologist at risk for incorrectly diagnosing recurrent melanoma while missing a second malignancy. We report a 69-year-old man with a history of acral melanoma, metastatic to inguinal nodes, presenting with an ipsilateral thigh nodule. Histology showed a proliferation of pleomorphic cells in the dermis and subcutis, suspicious for melanoma. S100, Melan-A, and HMB-45 immunohistochemistry were negative. However, microphthalmia-associated transcription factor and CD117 labeled the neoplasm, prompting consideration of a late metastatic melanoma with loss of antigen expression. Subsequent immunolabeling for CD4, CD43, and CD30 and clonal T-cell gene rearrangements enabled the correct diagnosis of cutaneous anaplastic large cell lymphoma. This case illustrates a pitfall in evaluating tumors in patients with known metastatic melanoma, and emphasizes the need for broad-spectrum immunohistochemistry in cases that are not clear-cut.
Departments of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA. pulitzem@mskcc.org
Melissa
M
Pulitzer
Mary Sue
MS
Brady
Elen
E
Blochin
Bijal
B
Amin
Julie
J
Teruya-Feldstein
D000368:Aged; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D017730:Ki-1 Antigen / Q000378:metabolism; D017728:Lymphoma, Large-Cell, Anaplastic / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology / Q000556:secondary; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology
D017730:Ki-1 Antigen; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D019009:Proto-Oncogene Proteins c-kit