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].