ALK-negative ALCL arising in a breast peri-implant capsule and associated seroma. a Low-power examination of the initial implant capsulectomy specimen reveals an apparent benign chronic inflammatory infiltrate in a background of dense fibrosis (H&E, ×40); however, atypical, but focally necrotic, large cells with hyperchromatic, irregular nuclei, and abundant eosinophilic cytoplasm are visible on high magnification (inset, H&E, ×400). b Large malignant-appearing cells with high nuclear-to-cytoplasmic ratios, prominent nucleoli, vacuolated cytoplasm, and mitotic figures are present in a cytospin of the seroma aspirate (Wright-Giemsa stain, ×1,000). c The second implant capsulectomy contains fibrosis, chronic inflammation, and more conspicuous clusters of large, atypical cells adjacent to the seroma cavity (H&E, ×100). d Viable clusters of large infiltrating cells have pleomorphic nuclei and prominent nucleoli with occasional “hallmark cells” present (H&E, ×400). e The implant capsule contains focal deposits of refringent, nonpolarizable material consistent with silicone adjacent to partially viable clusters of large atypical cells (H&E, ×400). f–h Immunohistochemical staining demonstrates the neoplastic cells to be positive for CD4 (f) and CD30 (g), but negative for ALK-1 (h; ×400). i T-cell receptor PCR identified a clonal rearrangement with Vγ10 primers (174.5 bp, blue tracing), as well as an indeterminate peak with Vγ1-8 primers (218.6 bp, green tracing), consistent with the presence of a clonal T-cell population

Hairy cell leukemia involving the bone marrow, breast, and axillary sentinel lymph node. a A posterior iliac crest bone marrow aspirate smear contains medium-sized lymphoid cells with oval nuclei, dispersed chromatin, and abundant pale cytoplasm with circumferential cytoplasmic projections (inset, Wright-Giemsa, ×1,000). CD20 stain of the core biopsy highlights the interstitial pattern of marrow involvement characteristic of hairy cell leukemia (×100). b–d Left breast lumpectomy containing prominent monomorphic infiltrates of small discohesive cells with abundant pale cytoplasm and round to oval nuclei present singly and in linear strands surrounding benign lobules (b; H&E, ×200), as larger clusters and aggregates surrounded by thin bands of fibrous stroma (c; H&E, ×400), as well as in solid sheets (d; H&E, ×400). DCIS was present elsewhere (not shown). e The sentinel lymph node shows massive replacement of the paracortex and hilum by cells with abundant pale eosinophilic cytoplasm and oval to spindled nuclei, morphologically similar to those in the breast (inset, H&E, ×400); residual primary follicles are present at the periphery of the node (H&E, ×20). f Immunohistochemistry of the breast specimen reveals infiltrating cells to be CD20-positive (inset) and strongly DBA.44-positive (×400). g Subsequent mastectomy demonstrates an infiltrate of monomorphic cells present singly and in loose linear arrays adjacent to residual cribriform DCIS (H&E, ×400). h–i A cytokeratin cocktail immunostain (h) of the mastectomy specimen highlights DCIS, but not the infiltrating cells, which are positive for CD20 (i; ×400)