Papillary thyroid carcinomas (PTC) are the most common thyroid tumors that usually have a good prognosis. The types of PTC associated with aggressive clinical behavior and significant mortality include tall cell, columnar cell, solid, diffuse sclerosing and hobnail variants. We present the clinicopathologic, features of a rare aggressive variant of the PTC showing elongated cells with a high nuclear/cytoplasmic ratio and a prominent hobnail features. The hobnail variant of Papillary Thyroid Carcinoma (PTC) was recently recognized and named.
Papillary thyroid carcinoma, Hobnail Variant
Papillary thyroid carcinomas (PTC) are the most common thyroid tumors that usually display an indolent clinical course. The morphologic variants of papillary carcinoma are papillary microcarcinoma, encapsulated variant, follicular variant, diffuse sclerosing variant, oncocytic (oxyphilic) variant, tall cell and columnar cell carcinoma, cribriformñmorular variant[1,2] However, a few patients with Papillary thyroid carcinomas (PTC) die of distant metastasis and radioactive iodine-refractory, progressive disease. The types of PTC associated with aggressive clinical behavior include tall cell, columnar cell, solid, diffuse sclerosing and hobnail variants. Here we present a case of papillary thyroid carcinoma with prominent hobnail features.
Case report :
A 25-year-old woman presented with a gradually progressive swelling on left side of the neck just lateral to the midline over three month. On palpation the swelling was (5cmx4cm) non tender originating from thyroid gland. The patient otherwise was asymptomatic. Her thyroid function test was normal. A Fine Needle Aspiration (FNA) of the mass with immediate assessment for specimen adequacy was performed. The cytologic diagnosis made as Papillary carcinoma. A preoperative ultrasound examination further characterized the tumor as an oval and irregular, heterogeneous, coarsened hypoechoic and vascular mass. The patient subsequently underwent - a total thyroidectomy. The specimen of thyroid gland and large lymph node over isthmus received after total thyroidectomy. Specimen consist of thyroid gland including left enlarged lobe, isthmus and right lobe.The left lobe measures 5.5cmx3.5cmx3cm. Right lobe measures 3cmX3cmX2cm. Isthmus measures 1.5cmX1cmX0.5cm. Cut surface of the left lobe shows unifocal nodular growth 3cmX2.5cm. The growth is grossly encapsulated. Cut surface of right lobe is unremarkable.
On microscopic examination, the tumor showed a predominantly papillary pattern with focal lymphocytic infiltration. The tumor cells had eosinophilic granular cytoplasm, intranuclear inclusions, irregular nuclear border, and nuclear grooves. Over 30% tumor cells contained eccentrically/apically located nuclei (a hobnail appearance). The tumour is partially capsulated margins are uninvolved. Section from left parathyroid gland is within normal limit. (1/1) lumph nodeis positive for metastasis. Pathological staging was-pT2pN1apMx
Fig-1. Papillae formation (10X)
Fig-2. Lymph node positive for metastasis(10X)
Fig-3. Prominent hobnail feature(40X)(Arrow)
The hobnail variant of Papillary Thyroid Carcinoma (HV-PTC) was recently recognized and named. HV-PTCs are characterized by loss of cellular polarity and discohesiveness, with tumor cells that exhibit a high N/C ratio. The nuclei are grooved and tend to be located toward the middle or apical portion of the cell, producing a surface bulge and imparting the so-called hobnail appearance.[4, 5] The hobnail cells vary in size and shape and, in extreme cases, can appear tall and columnar. This characteristic hobnail morphology has been described previously in a variety of tumors, both benign and malignant, including serous and clear cell carcinomas of the ovary, primary peritoneal serous carcinomas, and micropapillary carcinomas of the breast, bladder, and lung. Psammoma bodies, necrosis, and lymphocytic infiltration are uncommon. Initially, the cutoff of 30% hobnail features present in a tumor necessary to classify it as an HV-PTC was chosen rather arbitrarily. However, in subsequent studies, it has been demonstrated that patients who have tumors with hobnail features present in < 30% of the tumor have a significantly better 5-year survival than those who have >30% hobnail features (91.7% vs 43.6%).
In 2009, Motosugi et al described a patient aged 57 years with an aggressive PTC that extensively infiltrated the thyroid gland and exhibited a prominent micropapillary architecture and hobnail features. Asioli et al formally described this aggressive variant of PTC as a PTC with prominent hobnail features in a series of 8 patients. In that original report, the hobnail variant of PTC (HV-PTC) was described as a nonsolid type of PTC in which < 10% of the tumor had tall-cell/columnar-cell or diffuse sclerosing features and >30% of the tumor exhibited hobnail features with loss of polarity/cohesiveness. In addition, the authors demonstrated that HV-PTC occurred in a slightly older patient population compared with classic PTC (57.6 years vs 48.3 years), was more common among female patients, exhibited extensive extrathyroidal extension and vascular and/or lymphatic invasion, and frequently involved lymph nodes at the time of diagnosis. Metastatic and/or recurrent disease were observed in 7 of 8 of the originally described patients; in that series, 50% of the patients died of disease. A a better patient management might benefit from its early pathological diagnosis.