Encounter with unusual tumor having classic cytomorphology presenting as neck mass

CASE REPORT

A 50-year-old woman complained of the right-sided neck swelling of 6 months duration. It was a gradually increasing 4x3 cm, soft-firm, non-tender, slightly mobile mass. On ultrasonogram (USG) neck, there was massive, necrotic lymphadenopathy which suggested the possibility of tuberculosis and a small (0.9 × 0.7 cm size) cystic lesion in the thyroid gland. The patient revealed a history of similar neck swelling 3 years back, which regressed completely after aspiration, reports of which were not available. The fine-needle aspiration cytology of neck mass yielded approximately 5 ml, thin, hemorrhagic fluid; the swelling regressed partially after aspiration. The procedure was repeated from the residual mass. The FNA smears from neck nodes are provided.

Q1: What is the possible diagnosis?

1. Metastasis of papillary thyroid carcinoma

2. Nasopharyngeal carcinoma

3. Follicular dendritic cell sarcoma

4. Lymphoma

5. Ectopic meningioma

Answer: (c) Follicular dendritic cell sarcoma

The literature search reveals that follicular dendritic cell (FDC) sarcoma usually display cellular smears presenting as thick syncytial groups, whorls, fascicles, or single cells intimately admixed with mature lymphocytes and plasma cells. The cytological features are better highlighted on May-Grunwald Giemsa (MGG) stain [Figure 1a]. The cells are round to oval, with mild-to-moderate pale wispy cytoplasm; indistinct cell borders [Figure 1b], round to oval to plump nuclei with fine chromatin, prominent nucleoli, and many stripped nuclei. Nuclear atypia is variable. Bilobed and multinucleated tumor cells can be seen. Nuclear grooves and intranuclear inclusions have also been reported [Figure 1c].^[1-4] Our case presented majority of the above described cytoarchitectural features. In addition, microfollicular arrangement and vague papilloid structures were also seen. The nuclei were hyperchromatic, however, prominent nucleoli were not observed [Figure 1d].

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Figure 1:

(a) FNA from cervical LN: Tumor cells seen as thick fragments and singly placed cells, intimately admixed with lymphocytes and plasma cells (May-Grunwald Giemsa [MGG], ×20). (b) Oval, plump to elongated cells with indistinct outline, moderate pale cytoplasm (Papanicolaou [PAP], ×20). (c) Nuclei are round, oval to plump with fine chromatin and prominent nuclear intranuclear inclusion and nuclear grooves (arrow) (Papanicolaou, ×40). (d) Vague microfollicular pattern and dissociated tumor cells (PAP, ×20).

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1. Considering the primary presentation of enlarged neck nodes, USG favoring solitary hypoechoic lesion in thyroid and cytomorphology of vague papillary structures, microfollicular pattern, [Figure 1d] nuclear grooves, and intranuclear inclusions highlighted under MGG stain [Figure 1c]; metastasis of papillary thyroid carcinoma is the most probable diagnosis. However, the classical features such as papillary structures with core, metaplastic cytoplasm, and stringy colloid were absent

2. The other differential diagnosis can be nasopharyngeal carcinoma (NPC) undifferentiated type, which it mimics clinically and presents as enlarged neck nodes. The smears reveal mostly dissociated and loose groups of cells with few enlarged pleomorphic and lobulated nuclei against a background of mature lymphocytes. The presence of nuclear grooves, inconspicuous nucleoli, and low mitotic count was against the diagnosis of NPC^[4]

3. Possibility of lymphoma Hodgkin’s type was less likely, the pointers for lymphoma can be presence few atypical cells with pleomorphic, lobulated nuclei, and admixture with lymphocytes, plasma cells, and eosinophils. However, classical Reed–Sternberg cells were absent

4. Ectopic meningioma can also be a likely differential, especially when clinical presentation is neck mass. The overlapping features were oval to plump to elongated cells with bland chromatin, inconspicuous nucleoli, and intranuclear inclusions. However, the absence of whorl formation and admixture of lymphocytes with tumor cell makes the possibility of conventional meningioma less likely.^[5]

Question 2: FDC sarcoma is categorized as

1. Low-grade malignancy

2. High-grade malignancy

3. Intermediate-grade malignancy

4. Benign tumor

Answer: (c) Intermediate-grade malignancy^[6]

Question 3: All are common extranodal sites of this condition except

1. GIT

2. Brain

3. Skin

4. Liver

Answer: (b) Brain^[7]

Question 4: Which of the following is false about poor prognostic factors of FDC sarcoma?

1. Tumor size >10 cm

2. Mitosis >5/10 hpf

3. Coagulation necrosis

4. Significant cellular atypia

Answer: (a) Tumor size more than 10 cm^[7,8]

Further work up of the case

The patient was investigated, further his CT scan revealed a right cervical lymphadenopathy, seen as multiple, enlarged lymph nodes with cystic component and single 9 × 7 mm, cyst in the right lobe of thyroid. It also revealed ipsilateral enlargement of tonsil measuring 3 × 3 cm and left para pharyngeal heterogeneous, enhancing, lobulated mass favoring lymph node metastasis. FNA from parapharyngeal lymph nodes yielded similar cytomorphological features as that from cervical nodes [Figure 2]. The tonsillar biopsy showed subepithelial tumor which composed of solid nests whorls and rare foci with storiform pattern of spindle to oval to plump cells, admixed with lymphoplasmacytic infiltrate [Figure 3]. The cells have scant to moderate pale cytoplasm and central round to oval vesicular nuclei with nucleoli in some. Occasional mitotic activity was noted. The histology was suggestive of FDC sarcoma. The tumor cells expressed CD21 membranous positivity and therefore substantiated the diagnosis of FDC sarcoma [Figure 4]. The patient underwent bilateral tonsillectomy with ipsilateral radical neck dissection. The contralateral tonsil was uninvolved by tumor while the cervical lymph nodes showed evidence of metastasis. Post-surgery, the patient received radiation therapy.

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Figure 2:

FNA from Para pharyngeal LN mass: Tumor cells with similar morphology with few scattered mature squamous cells (Hematoxylin and eosin, ×20).

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Figure 3:

Tonsillar mass Histopathology: Subepithelial tumor consisting of solid islands and fascicles separated by fibrous stroma having mononuclear cell infiltration. Cells are round to oval with moderate pale cytoplasm, central nuclei with vesicular chromatin, and nucleoli in some. Occasional pleomorphic cells also evident (Hematoxylin and eosin, ×20).

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Figure 4:

Immunohistochemistry: Tumor cells expressing strong membranous positivity (CD21, ×20).

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