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Crystal-storing histiocytosis (CSH) is a rare non-neoplastic histiocytic lesion with abnormal accumulation of immunoglobulin (Ig) light chain. CSH is associated with Ig overproduction by B-lymphoproliferative disorders (B-LPDs) or by persistent inflammatory diseases. Eighteen cases of pulmonary CSH have been reported. However, no case reports of tracheal CSH have been published. In this patient, we found a solitary tracheal tumor in an asymptomatic 60-year-old man on chest computed tomography scan. Histologically, the tumor comprised two different lesions. One lesion showed diffuse proliferation of spindle-shaped histiocytes with abundant eosinophilic granular cytoplasm. With immunohistochemistry, the histiocytic cells were positive for CD68, CD163 and Ig kappa light chain, and the cytoplasm was weakly positive for anaplastic lymphoma kinase (ALK) protein. Fluorescence in situ hybridization indicated no split signals for the ALK gene. Electron microscopy demonstrated many elongated or rhomboid-shaped dense crystals in the cytoplasm of histiocytes. The second lesion showed proliferation of CD20-positive small atypical lymphocytes mixed with Ig kappa chain-positive plasma cells. A diagnosis of CSH and concomitant mucosa-associated lymphoid tissue lymphoma was made. In this patient, unexpected ALK protein was detected in infiltrating histiocytes. Therefore, careful assessment of the ALK protein and gene was necessary to differentiate from other histiocytic disorders. [ABSTRACT FROM AUTHOR]

We report a case of ALK-positive renal cell carcinoma coincident with Hodgkin lymphoma. The patient was a 19 year-old-girl without sickle cell trait. The right renal tumor was discovered concomitantly with Hodgkin lymphoma (HL). After chemotherapy for HL, right nephrectomy was performed. Microscopically, the tumor showed a solid and focally pseudo-papillary growth pattern studded with tubular structures. Most tumor cells were small bland eosinophilic cells, but rhabdoid cells, vacuolated cells, pleomorphic multinucleated giant cells were also admixed. The variety of growth patterns and cell features led us to speculate a possibility of ALK-positive renal cell carcinoma (ALK + RCC). ALK was immunohistochemically positive, and fluorescence in situ hybridization analysis detected a split signal of the ALK gene. We examined previously reported partner genes (STRN, TPM3, VCL and EML4) by RT-PCR, but fusion gene was not detected. RCC showing solid or cribriform growth patterns with vacuolated cells with intracytoplamic lumina, rhabdoid cells, and mucus production indicates the possibility of ALK + RCC. [ABSTRACT FROM AUTHOR]