Diffuse sclerosing variant of papillary thyroid carcinoma--a rare cause of goitre in a young patient.

Editor,

Papillary thyroid carcinoma is the most common thyroid malignancy. We report a case of a rare variant - diffuse sclerosing papillary thyroid carcinoma (DSPC).

Case History

An 18 year old girl presented with a smooth symmetrical goitre. She was clinically euthyroid and had no palpable cervical lymph nodes. Thyroid function tests and anti-thyroid peroxidase level were normal. Ultrasound scan of thyroid showed marked nodular enlargement of the entire gland in keeping with a multinodular goitre. A hypoechoic 1cm nodule was identified at the right lobe which was found to be ‘cold’ on radio-isotope scanning. A fine needle aspiration of this ‘cold’ nodule was reported as papillary carcinoma.

She was booked for total thyroidectomy. At surgery she had an enlarged thyroid, with a gross appearance in keeping with a thyroidititis or lymphoma. Frozen section confirmed papillary carcinoma. The gland was hard and gritty. Several local lymph nodes were also excised. Post-operative recovery was uneventful.

Sectioning revealed a diffusely firm, white, gritty gland (fig 1). Histopathology showed this to be the rare diffuse sclerosing variant of papillary thyroid carcinoma. Scattered islands of tumour tissue, squamous metaplasia, stromal sclerosis, heavy lymphoplastic infiltrate and abundant psammoma bodies were found diffusely throughout both lobes and through the capsule (fig 2). All excised lymph nodes contained metastatic carcinoma.

Fig 1

Sclerotic hemisection of thyroid lobe

Fig 2

Papillary carcinoma, with psammoma bodies and squamous metaplasia. Sclerosis and chronic inflammation, to right of field. (× 200)

She underwent radioablative therapy followed by replacement levothyroxine. There was no residual uptake on subsequent 123-Iodine isotope scanning.

Discussion

First described in 1985, diffuse sclerosing papillary carcinoma of the thyroid (DSPC) is a rare variant malignancy, recently reported to account for 0.8% of papillary thyroid carcinomas.1,2 Patients present with a diffuse goitre and are mostly clinically euthyroid, but can also be hypothyroid or hyperthyroid. It occurs most frequently in young females and may be mistaken clinically for benign disease particularly thyroiditis.3–5 Most patients have lymph node metastases at the time of diagnosis and lung metastases are common.3 Cerebral metastases have also been reported.6

The presence of several pathological characteristics is diagnostic: diffuse firm enlargement of the thyroid gland, scattered islands of papillary carcinoma, extensive lymphatic permeation and lymphocytic infiltration, squamous metaplasia, sclerosis and numerous psammoma bodies.7 Detection of abundant psammoma bodies on ultrasonography may provide pre-operative evidence of DSPC.4 This could facilitate improved surgical planning for a technically challenging thyroidectomy.

Early studies suggested that DSPC had a poorer prognosis than classical papillary carcinoma due to its aggressive nature with frequent lymph node and distant metastases at the time of presentation. It had also been reported that eradication required a more aggressive therapeutic approach.3 However, more recent studies suggest that DSPC patients have a similar prognosis and that the treatment should be that for classical papillary thyroid carcinoma i.e. radical surgery, radio-iodine ablation and/or external radiotherapy.2,8

There are potential pitfalls which may delay the diagnosis of DSPC. In this case, the clinical presentation, biochemical, serological and initial radiological findings were all indicative of benign pathology. FNA indicated malignancy leading to surgery demonstrating its importance in the diagnosis of DSPC. As metastases are frequently present it is therefore important to consider this rare malignancy when investigating a goitre in a young patient.