Abstract

Primary cutaneous anaplastic large cell lymphoma (PCALCL) is a CD30-positive T-cell lymphoproliferative disorder (LPD) that is limited to the skin. Expression of anaplastic lymphoma kinase (ALK) is exceedingly rare in PCALCL but is seen in most cases of systemic ALCL. The histopathologic findings in PCALCL and systemic ALCL are identical. For these reasons, recognition of ALK+ PCALCL is challenging and requires careful clinical-pathologic correlation. A 22-year-old woman presented with a 2-month history of a 5.0 cm ulcerated plaque on her left lower back. Biopsy showed sheets of large, atypical lymphoid cells with irregular nuclear contours, vesicular chromatin, and prominent nucleoli. These cells expressed CD2 and CD30 and a subset expressed CD4; CD5 and CD7 were negative. ALK displayed cytoplasmic positivity. The patient had no lymphadenopathy and LDH was within normal limits. Bone marrow biopsy did not reveal systemic disease, but PET/CT demonstrated multiple small, mildly avid lymph nodes in the cervical, axillary, tonsillar and inguinal regions. The patient received 6 cycles of brentuximab-vedotin, cyclophosphamide, doxorubicin, and prednisone (BV-CHP) for presumed systemic disease. One month later, the patient developed multiple papules and nodules on the extremities. Biopsy showed recurrent ALK+/CD30+ T-cells. Repeat PET/CT redemonstrated the previous findings without significant interval change. The patient’s skin lesions completely and spontaneously regressed over weeks without recurrence for 28 months. The patient’s clinical and pathologic findings indicate ALK+ PCALCL. ALK+ PCALCL has a favorable prognosis like other PCALCL and does not require systemic chemotherapy. Importantly, the histopathologic features overlap with systemic disease, requiring careful clinical-pathologic correlation.