Case Report: Phenotypic Switch in High-Grade B-Cell Lymphoma With MYC and BCL6 Rearrangements: A Potential Mechanism of Therapeutic Resistance in Lymphoma?

Lineage switch between myeloid and lymphoid in acute leukemia is well established as a mechanism for leukemic cells to escape chemotherapy. Cross-lineage transformation is also recognized in some solid tumors on targeted therapy, such as adenocarcinomas of the lung and prostate that transforms to neuroendocrine carcinoma on targeted therapy. Now lineage plasticity is increasingly recognized in mature lymphomas, such as small B-cell lymphomas transforming to histiocytic/dendritic cell sarcoma. However, there is no report of aggressive mature B-cell lymphoma switching from one histologic category to another upon targeted therapy. We report here a case of high-grade B-cell lymphoma with MYC and BCL6 rearrangements relapsing as a high-grade plasmablastic neoplasm with MYC and BCL6 rearrangements after R-CHOP and R-EPOCH therapy. Being aware of this rare scenario will help improve our understanding of the underlying mechanisms of therapeutic resistance and progression of lymphoma.

Corrigendum: Not always ‘squame’: The rare entity of follicular dendritic cell sarcoma of the tonsil presenting with cervical nodal metastases

No abstract available.

Follicular Dendritic Cell Sarcoma of the Thyroid Gland in a Patient with Preexisting Hashimoto’s Thyroiditis: A Rare Case Report with a Literature Review

Thyroid follicular dendritic cell sarcoma (FDCS) is an extremely rare malignancy that originates from follicular dendritic cells of the thyroid germinal centers. To the best of our knowledge, there are only 4 reported cases of thyroid FDCS in the English literature. Herein, we present the fifth case of FDCS of the thyroid gland. A 63-year-old woman presented with a painless midline neck mass, enlarging for the last 4 months. Physical examination revealed a 6-cm nonmobile, firm, multinodular thyroid mass with palpable cervical lymphadenopathy. Due to high suspicion for thyroid malignancy, the patient underwent total thyroidectomy with bilateral modified radical neck dissection. Histologic evaluations revealed sheets of storiform eosinophilic tumoral cells with prominent nucleoli containing multinucleated giant cells, and subsequent immunohistochemistry showed immunoreactivity for CD4, CD21, CD35, CD45 (LCA), and CD68. The patient was started on 6 cycles of doxorubicin, ifosfamide, and radiotherapy. She has had monthly thyroid ultrasonography and contrast-enhanced thoracoabdominal CT scan every 3 months for detecting potential recurrence and/or metastasis screening. Fortunately, 8 months after the operation, the patient is alive without any signs of local or distant metastasis.

Concomitant malignancies in the neck: follicular dendritic cell sarcoma; a rare tumour presenting as a right-sided neck nodal mass and papillary carcinoma thyroid

Follicular dendritic cell sarcoma is a rare low-grade sarcoma of mesenchymal origin. It involves the lymph nodes more commonly and rarely extranodal sites. The most common lymph node is cervical and usually presents as a painless asymptomatic mass. More often, it is a misdiagnosis, and there is a delay in treatment. It is rarely associated with Castleman disease, myasthenia gravis. Diagnosis of this condition is by histopathology and immunochemistry. Surgery is the primary modality of treatment, and adjuvant therapy has been tried with no definite trials due to the rarity of the disease. Here, we report a case of concomitant follicular dendritic sarcoma of the right cervical lymph node and papillary carcinoma of the thyroid managed in our institute. There was a line of investigations approaching towards a diagnosis, and she underwent total thyroidectomy and right modified radical neck dissection.

Interdigitating dendritic cell sarcoma located in the adrenal gland: a case report and literature review

We report a case of interdigitating dendritic cell sarcoma (IDCS) originating from the adrenal gland. A 57-year-old middle-aged woman with no previous history of malignancy came to our hospital after color Doppler ultrasound revealed a right adrenal mass. An abdominal computed tomography scan also showed an adrenal mass. Postoperative pathology confirmed the diagnosis of IDCS. After complete surgical removal of the adrenal tumor, the patient has been disease-free for 1 year. IDCS may have a good prognosis after surgical resection. To our knowledge, this is only the second reported case of IDCS in the adrenal region.

Follicular dendritic cell sarcoma of liver: a rare case report

Follicular dendritic cell sarcoma (FDCS) most commonly involves lymph nodes but also affects extranodal sites like liver, spleen, pancreas less commonly. It is a low to intermediate grade malignancy. Unusual presentation, morphology or immunophenotyping makes the diagnosis of FDCS very challenging. Immunohistochemistry plays a major role in confirming the diagnosis of FDCS. A 40 year male presented with dull abdominal pain. Ultrasonography revealed two hypoechoiec lesions in liver. Cytomorphology, later histological and immunohistochemistry (IHC) diagnosis of FDCS was established. Patient was put on chemotherapy.

Mimics of carcinoma: pancytokeratin positive follicular dendritic cell sarcoma

Introduction/Objective Follicular dendritic cell sarcoma (FDC-S) is a malignant neoplasm of follicular dendritic cells that can present with variable morphology including epithelioid and spindle cell components. Given its morphological diversity, FDC-S can mimic neoplasms including poorly differentiated carcinomas. Here we present a rare case of FDC-S in which immunohistochemical staining for pancytokeratin was focally positive, potentially leading to an erroneous diagnosis if a full spectrum of immunohistochemical stains was not considered. Methods/Case Report A 34-year-old man presented with an enlarging left neck mass, night sweats and fatigue that began approximately three months ago. CT scan showed a 5.6 x 4.2 x 3.7 cm necrotic mass in the left upper lateral carotid space. Histologic examination of the incisional biopsy specimen demonstrated portions of soft tissue comprised of pleomorphic and plump spindle cells forming whorls with no discernable node architecture (Panels A-B). The tumor cells are large with oval nuclei, vesicular chromatin, distinct nucleoli, and a moderate amount of eosinophilic cytoplasm. Occasional binucleated and multinucleated tumor cells, rare tumor cells with nuclear pseudoinclusions and atypical mitotic figures, and focal necrosis are identified. Scattered small mature lymphocytes are present. By immunohistochemistry, tumor cells are positive for pancytokeratin (focal) (Panel C), CD21 (panel D), CD23 (panel E), D2-40 (panel F), CD35 and clusterin, and negative for CD3, CD20, CD30, CD45, ALK-1, EMA, PAX5, PDL1 and S100 stains. The overall morphology and immunostaining pattern are compatible with follicular dendritic cell (FDC) sarcoma. Results (if a Case Study enter NA) NA Conclusion FDC sarcoma rarely occurs as the solitary mass in the head and neck region. The unusual focal positivity for pancytokeratin highlights the importance of comprehensive immunohistochemistry stains to confirm the diagnosis of FDC sarcoma since this case is focally positive for pancytokeratin, mimicking other neoplasms such as poorly differentiated carcinomas

A Challenging and Rare Case of Metastatic Follicular Dendritic Cell Sarcoma Originating from a Tonsil

Introduction/Objective Follicular dendritic cell sarcoma (FDCS) is a rare malignant tumor of follicular dendritic cells. Most cases of FDCS are described in lymph nodes, but it can involve extra-nodal locations such as the tonsil. Methods/Case Report We report a case of a 55-year-old male with a 6-month history of a slow growing left neck mass. The patient had a poorly differentiated carcinoma of the left tonsil diagnosed based on morphologic features eight years ago, followed by chemoradiation, and subsequent left tonsillectomy without tumor identified. Imaging reported a 4.0 cm mass in the left neck level III lymph node location. Biopsy of the mass revealed a spindle cell neoplasm. It was difficult to reach a definitive diagnosis despite an extensive work-up. Review of the previous left tonsil biopsy showed a pleomorphic epithelioid cell proliferation. On the radical resection specimen of the left neck mass, a 4.5 cm, tan-gray, fleshy, necrotic mass was present. Microscopically, it demonstrated a neoplasm with spindle cell and epithelioid cell proliferation, with extensive necrosis. A wide panel of immunostains was performed; the tumor cells showed positivity for CD21, CD23, CD35, and focally weak positivity for cytokeratin OSCAR and Synaptophysin. Squamous cell markers were negative. These findings are consistent with FDCS. Further work-up on the original tonsil tumor displayed immunostaining profile of FDCS. This case was consulted with the National Institute of Health (NIH) for confirmation of the diagnosis. Results (if a Case Study enter NA) NA Conclusion Morphologically, FDCS can present with various histologic patterns, which can lead to diagnostic pitfalls, and common confusion with poorly differentiated carcinoma or soft tissue tumors, especially in needle biopsies. Generally, patients present with a prolonged clinical course, with a 50% and 25% chance of recurrence and metastasis respectively, hence the awareness and accurate diagnosis of this entity is important in biopsies of lymph nodes or of extranodal locations such as a tonsil.