Discussion:
Although tuberculosis and cancer are two completely different diseases, they can present with unusual but similar symptoms that may overlap and mimic each other. In fact, misdiagnosis of cancer and tuberculosis has been reported in various organs, such as the lungs, liver, breast, bones, and even the thyroid gland [1]. It is more common for thyroid tuberculosis to be misdiagnosed as thyroid cancer than the opposite [2,3]. Many cases of thyroid tuberculosis wrongly diagnosed as thyroid cancer have been associated with pressure symptoms such as dysphagia [16], dyspnea, and recurrent laryngeal nerve palsy [17], raising suspicion of malignancy. However, it is very unusual for thyroid cancer to present as cervical tuberculosis. In our case, tuberculosis was suspected due to the insidious progression of the cervical swelling, the appearance of cutaneous fistula with the discharge of pus and whitish material reminiscent of tuberculous caseum as well as the central necrosis of the mass on CT scan while taking into consideration the high prevalence of tuberculosis in the country.
Anaplastic thyroid carcinoma represents approximately 2% of all thyroid cancers [7]. It is a particularly dreaded form of cancer due to its extreme aggressiveness and poor prognosis. It most commonly in the elderly, with a mean age distribution between 60 and 79 years and is slightly more common among women (1.5 - 2 ratio) [7].
Anaplastic carcinoma is thought to arise from a terminal dedifferentiation of preexisting carcinomas of the thyroid follicular cell. This association has long been suggested by the consistent observation of coexisting follicular or papillary thyroid carcinomas with anaplastic carcinoma [8]. The classic presentation of anaplastic thyroid carcinoma is a rapidly growing large goiter or nodule that is firm to the touch and fixed to underlying structures [9]. Signs of local-regional invasion are common, including inspiratory dyspnea, dysphonia due to recurrent laryngeal nerve paralysis, dysphagia, and cervical pain. More than 80% of patients have cervical lymph node metastasis at presentation, and 20 to 50% have systemic metastasis [10].
Case reports of unusual presentations of anaplastic thyroid carcinoma include possible bradycardia due to compression of the vagus nerve [11], superior vena cava syndrome [12], thyrotoxicosis [13], acute Horner syndrome [14], leukocytosis from granulocyte colony-stimulating factor secretion and ball valve-type respiratory obstruction [15]. The presentation of anaplastic thyroid carcinoma mimicking cervical tuberculosis is very unusual and may be the first case reported in the literature.
Even the rare similar cases reported in the literature were thyroid carcinomas mimicking the presentation of cervical abscess rather than tuberculosis [4,5,6]. In fact, Loh TL et al. [4] reported a rare case in 2018 of anaplastic thyroid carcinoma mimicking a thyroid abscess in a 52-year-old patient. Fine needle aspiration cytology was negative for malignancy. An incision and drainage were performed and histopathology result of a proximal isolated enlarged lymph node biopsied revealed metastatic carcinoma. Thyroid biopsy confirmed anaplastic thyroid carcinoma. Mahattanapreut et Al. [5] Reported in 2021 a case 67-year-old patient presented with a large abscess involving the retropharyngeal space, oro-hypopharynx, larynx, and left lobe of the thyroid gland with multiple lymphadenopathies with cystic necrosis. The patient underwent incision and drainage of the abscess and necrotic tissue samples were sent for histopathology. Papillary thyroid carcinoma was found in the pathology of the necrotic tissue with lymph node metastasis. Lin et al. [6] conducted a study on the incidence of head and neck cancers presenting initially as deep neck infections. Among the 81 patients with deep neck infections, 4 were found to have underlying cancers, including papillary thyroid carcinoma, nasopharyngeal carcinoma, hypopharyngeal carcinoma, and Hodgkin’s lymphoma.
To distinguish between the infectious process and malignancy, fine needle aspiration cytology should be performed [18]. However, cytological examination of the cystic lesions of malignancy might yield a false negative result because of the dilutional effect of cystic fluid. In our case, even the biopsy of the abscess wall was initially negative. This can be attributed to the abundance of inflammatory cells, as the presence of a few atypical clusters of cells may go unnoticed [18].
The literature supporting specific guidelines for the treatment of anaplastic thyroid cancer is limited. Therapeutic options include surgery, radiation, and systemic therapy [19]. Similarly, incision and drainage of the cervical abscess underlying the tumor is part of the treatment, although it may seed the tumor into the soft tissues of the neck and skin as loculations are broken down, and encourage the dissemination of carcinoma cells [18].
Surgical removal of this rapidly progressing cancer is often not possible due to either extensive local disease or synchronous metastatic disease. Total thyroidectomy has been reported to increase survival rates in highly selected cases; however, cervical and mediastinal disease must be minimal [20].
The most critical aspect of therapy is controlling the local spread of the disease and its associated symptoms. Although anaplastic thyroid cancer has been considered radioresistant compared to other malignancies, several studies have shown that radiotherapy can effectively control local disease and alleviate symptoms in some cases [21]. Lastly, systemic therapy can be used to reduce the overall disease burden, although contemporary chemotherapy regimens have not been proven to affect overall survival. Anaplastic thyroid carcinoma is known for its poor prognosis. The 5-year survival rate is less than 10%, and the average survival is 6 to 8 months regardless of treatment [19].