A case report to illustrate the challenging nature of differentiating inflammatory phase of morphea from cutaneous lymphoproliferative neoplasm in the setting of patient with known history of scleroderma.

Summary: A 71-year-old-female with history of rheumatoid arthritis, sclerodactyly without systemic sclerosis, and extra-nodal marginal zone B cell lymphoproliferative disorder (2012 right breast, 2016 right thigh status post rituximab followed by ibrutinib and 6 cycles of R-CHOP; remission noted 2018) presented with changes in a plaque that had been present for years. Examination showed two linear atrophic plaques on the right posterior buttock. Punch biopsy demonstrated thickening of pan-dermal collagen. CD34-immunostain revealed loss of the expected interstitial pattern. There was also a superficial to deep dermal patchy infiltrate of mildly enlarged mononuclear cells with plasma cells . CD20 and BCL2 were positive, and the plasma cells showed Lambda restriction with in-situ hybridization. These findings were consistent with cutaneous marginal zone lymphoproliferative disorder (PCMZLPD), and the background features were most consistent with morphea. The patient was started on Zanubrutinib in early May with improvement noted during follow-up visits. This case elaborates on the challenging nature of differentiating the inflammatory phase of morphea from a cutaneous lymphoproliferative neoplasm. We propose that the patient may have developed morphea in the region of recurrent PCMZLPD due to prior treatments for her loco-regional history of PCMZLPD disorder in 2016.