Intravascular large B-cell lymphoma arising in the pituitary gland: A case report.

RATIONALE: Primary pituitary lymphoma is defined as a lymphoma that develops only in the pituitary gland without involvement of other areas.

PATIENT CONCERNS: We present the case of a 61-year-old female patient who underwent an endonasal transsphenoidal approach for the preoperative diagnosis of a pituitary macroadenoma based on radiological findings.

DIAGNOSES: Microscopically, the capillaries were distended by tumor cells. The high-magnification view showed large cells with vesicular nuclei and single or multiple prominent nucleoli, with mitotic figures often observed within the intravascular space.

INTERVENTIONS: Immunohistochemical staining showed strong positivity for CD45 and pan-B cell markers such as CD19 and CD20. The postoperative diagnosis was intravascular large B-cell lymphoma of the pituitary gland.

OUTCOMES: Next-generation sequencing revealed alterations in 12 genes: ARID5B, BCL2, CD79B, ETV6, HLA-B, LRRC7, MYD88, PIM1, POT1, PTPN11, RASA1, and SRSF2.

LESSONS: To our knowledge, this is the first case report of pituitary intravascular large B-cell lymphoma.