PAPILLARY CARCINOMA, FOLLICULAR VARIANT, IN A BACKGROUND OF LYMPHOCYTIC (HASHIMOTO'S) THYROIDITIS

Case provided by Amy Stein, MD

Case History

A 50 year old woman with a right-sided thyroid mass which was noted by the patient and was palpable on physical examination.  On ultrasound, the right lobe of the thyroid showed a 12 mm mass.  A fine needle aspirate was performed and subsequently a total thyroidectomy was done.

Microscopic Findings

The fine needle aspiration was processed using the SurePath liquid-based preparation to create a thin-layer slide.  The slide shows crowded groups of follicular cells, some with rounded papillary configurations.  The cells are enlarged and both intranuclear pseudoinclusions and nuclear grooves are seen.  There were occasional lymphocytes and plasma cells noted which raised the possibility of underlying lymphocytic thyroiditis.  The right side of the thyroid shows a fairly well-circumscribed though unencapsulated 1 cm nodule.  The nodule has a follicular architecture comprised of crowded enlarged follicular cells.  The nuclei show pale chromatin, described as an “Orphan Annie Eye” appearance.  There are nuclear grooves and rare intranuclear pseudoinclusions.  The background thyroid tissue shows marked chronic inflammation with germinal centers and the residual thyroid follicles show follicular cells with the abundant pink staining granular cytoplasm of oncocytic cells.  These latter findings represent lymphocytic (Hashimoto’s) thyroiditis.

Diagnosis

PAPILLARY CARCINOMA, FOLLICULAR VARIANT , IN A BACKGROUND OF LYMPHOCYTIC (HASHIMOTO’S) THYROIDITIS

Discussion

Papillary carcinoma is the most frequent type of thyroid carcinoma and the follicular variant represents 15-20% of cases.  Histologically, the follicular variant of papillary carcinoma has a complete absence of papillary formation and instead shows a follicular architecture.  It is identifiable as a papillary carcinoma based upon the presence of the characteristic cytologic features of papillary carcinoma, namely the optically clear nuclei and the presence of intranuclear cytoplasmic pseudoinclusions and nuclear grooves.  The infiltrative follicular variant shows similar clinical behavior to classic papillary carcinoma unlike the encapsulated follicular variant which behaves more similarly to follicular adenoma.  Similar to these clinical findings, the infiltrative follicular variant shows a high rate of BRAF mutations as are seen in papillary carcinoma, while the encapsulated follicular variant shows a high rate of RAS mutations like follicular adenoma/carcinoma.  Although some studies have shown a higher incidence of papillary carcinoma in patients with Hashimoto’s thyroiditis, case-control and large retrospective cohort studies have not confirmed an association.

 The patient is scheduled for a follow-up appointment with a consulting endocrinologist two months after surgery.

References

  1. Nikiforov, YE.  Diagnostic Pathology and Molecular Genetics of the Thyroid. Philadelphia:  Lippincott Williams & Wilkins, 2009:  160-182.
  2. Rivera, M, et al.  “Molecular genotyping of papillary thyroid carcinoma follicular variant according to its histological subtypes (encapsulated vs infiltrative) reveals distinct BRAF and RAS mutation patterns.”  Mod Pathol 2010; 23:1191-1200.
  3. Revera, M, et al.  “Encapsulated thyroid tumors of follicular cell origin with high grade features (high mitotic rate/tumor necrosis):  a clinicopathologic and molecular study.”  Hum Pathol 2010: 41: 172-180.
  4. Liu, J, et al.  “Follicular variant of papillary thyroid carcinoma:  a clinicopathologic study of a problematic entity.  Cancer 2006; 107: 1255-1264.

 

 

 

SurePath™ Smear: Follicular groups in background of scattered Lymphocytes
SurePath™ Smear; High Power Magnification: Occasional follicular cells show intranuclear inclusions
SurePath™ Smear; High Power Magnification: Follicular cells with occasional nuclear grooves
SurePath™ Smear; High Power Magnification: Occasional follicular cells show intranuclear inclusions
H&E Stain; Low Power Magnification: Macrofollicles with hypereosinophilic colloid
H&E Stain: Follicular variant of papillary carcinoma
H&E Stain; High Power Magnification: Occasional cells with nuclear grooves
H&E Stain; High Power Magnification: Occasional cells with nuclear grooves
H&E Stain; High Power Magnification: Marked nuclear clearing (Orphan Annie Eyes)
H&E Stain: Neoplastic follicular cells with fine dusty chromatin
H&E Stain; High Power Magnification: Nuclear clearing (Orphan Annie Eyes)
H&E Stain; High Power Magnification: Fine dusty nuclear chromatin